Device for controlling at least one switchable valve

ABSTRACT

A method for controlling at least one switchable valve, a brake impulse that slows down the valve movement being produced during the controlling of the at least one valve, the position and/or the length of the brake impulse being specified as a function of a switching time of the valve, it being checked whether a characteristic feature occurs that indicates the switching time, and, upon occurrence of the characteristic feature, the position and/or the length of the brake impulse being adapted based on the position of the characteristic feature.

BACKGROUND INFORMATION

German Patent Application No. DE 10 2009 000 132 A1 describes a method for controlling at least one switchable valve. There, in the controlling of the at least one valve a brake impulse is produced that slows down the valve movement. The position and/or the length of the brake impulse are specified as a function of a switching time of the valve. The effect on the switching noise here is essentially a function of the position and the duration of the brake impulse.

If the brake impulse does not take place at the right time and with the right duration, it does not deploy its full effectiveness. In the extreme case, it has no effect. Based on changing conditions and/or aging effects at the valve, the time changes at which the switching time occurs. With this the time also changes at which the brake impulse deploys its full effectiveness.

SUMMARY

An method according to the present invention may have the advantage that the noise effect is maintained even as boundary conditions change, such as the voltage at the valve, the fuel pressure, and the temperature.

This may be advantageously achieved in accordance with the present invention by checking whether a characteristic feature occurs that indicates for example the flight characteristic of the valve needle, and when the characteristic feature occurs, the position and/or the length of the brake impulse is adapted on the basis of the position of the characteristic feature.

It is particularly advantageous if, based on the characteristic feature, a corrected position and/or length of the brake impulse is ascertained.

In an improved specific embodiment, the position and/or the length of the brake impulse is specified as a function of further characteristic quantities, such as the temperature, the pressure, and/or the voltage. In this way, a more precise specification of the brake impulse is possible.

It is particularly advantageous if a switching time is used as characteristic feature. At the switching time, the valve needle reaches its impact. Ideally, the brake impulse is triggered shortly before reaching the switching time.

The characteristic feature can be ascertained particularly simply if the characteristic feature is a bend in the voltage curve or in the current curve, recognized on the basis of the first derivative of the voltage curve or current curve.

It is particularly advantageous if the switching time is recognized based on the second derivative of the voltage curve.

In a particularly advantageous specific embodiment, the characteristic feature is the beginning of a flight phase of the valve needle. The beginning of the flight phase is situated before the position of the brake impulse and is therefore not influenced by it. Therefore, this characteristic feature can also be ascertained when a controlling with brake impulse takes place.

Further advantageous embodiments are described herein.

It is particularly advantageous that the beginning of the flight phase is recognized from the first derivative of the current curve.

In a further aspect, the present invention relates to program code together with processing instructions for creating a computer program that can be executed on a control device, in particular source code having compiler and/or linking instructions, the program code resulting in the computer program for executing all steps of one of the described methods when it is converted into an executable computer program according to the processing instructions, i.e., in particular is compiled and/or linked. This program code can be given in particular by source code, which can be downloaded for example from a server in the Internet.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are shown in the figures and are explained in more detail below.

FIG. 1 shows the main elements of a device for controlling a valve.

FIG. 2 shows various signals plotted over time.

FIGS. 3 through 6 show current curves and/or voltage curves of various specific embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In FIG. 1, a device is shown for controlling a valve 100. In the depicted specific embodiment, valve 100 is connected in series with a switch 110 and a measurement device 120, between the two terminals 130 and 135 of a power supply. A control device 140 supplies switch 110 with a control signal A. Measurement device 120 supplies control device 140 with a measurement quantity. In addition, sensors 150 are provided that forward sensor signals to control device 140.

The sequence and the number of elements connected in series are shown only as examples. Measurement device 120, switch 110, and valve 100 can also be configured in a different sequence. In addition, it can be provided that a further switch or other circuit elements are provided.

Control device 140 calculates, based on various sensor signals and further quantities present in the control device, a control signal A to be supplied to switch 110. A current flows through valve 100 as a function of the position of switch 110. As a function of the current, a voltage drop arises at the valve. Current measurement device 120 measures in particular the current flowing through valve 100. Alternatively, it can also be provided that the voltage drop at valve 100 is acquired using a suitable measurement device 120.

When the valve is opened or closed due to being supplied with current, switching noises occur. These switching noises can be significantly reduced by interrupting the controlling during switching on or by a brief re-switching on after switching off. The effect on the switching noise here is a function of the time and the duration of these two so-called brake impulses.

In FIG. 2a , control signal A is plotted over time t. In FIG. 2b , the stroke H of the valve is plotted, and in FIG. 2c the current I flowing through the valve is plotted. At time t0, the controlling of the valve begins. Starting from this time, control signal A is present at switch 110. Current I through the valve increases with time. At a time t1, control signal A is interrupted, and is switched on again at time t2. This has the consequence that the current drops off between times t1 and t2. This time t1 is chosen such that between times t1 and t2 the valve needle moves in the direction of its new position. At time t3, control signal A is withdrawn in order to end the injection. Starting from time t3, the current decreases and the valve needle moves slowly back to its initial position. At time t4, switch 110 is again controlled, this controlling ending at time t5; i.e., the flow of current is switched on again between times t4 and t5.

The first time duration, between times t0 and t1, in which current is supplied to the valve is designated ITO. The second time duration, in which current is supplied to the valve between times t2 and t3, is designated IT1. The third time duration in which current is supplied to the valves, between times t4 and t5, is designated IT2. In the first pause time P0 between times t1 and t2, the valve is switched off. In the second pause time P1 between times t3 and t4, the valve is also switched off.

In FIG. 3 current curve I is plotted over time t. The switch-on process is shown with the beginning of the supply of current. At time t0, the controlling of the flow of current through the valve thus begins. First, the current increases. As soon as the valve needle begins to move, the inductance of the valve changes and the current flow deviates from its previous curve. In the depicted specific embodiment, it is even the case that the current briefly decreases. When the valve needle reaches its stop, the current increase again changes. This happens at time ts. The interval between the beginning of the supply of current at time t0 and this switching time ts is designated opening delay tan. The specific current curve during the opening process differs from magnetic valve to magnetic valve. However, in all magnetic valves there occurs a characteristic feature that indicates the switching time. In the specific embodiment depicted in FIG. 3, the characteristic feature is the bend in the current curve at time ts. In most valves, the current curve has a bend or a similar feature at the switching time. A corresponding feature also occurs at the termination of the controlling. The time duration between the termination of the controlling of the closing of the valve is designated closing delay tab. Here, a corresponding feature can be determined from the curve of the induction voltage of the valve.

Alternatively, the switch-off time can be made visible in the current signal through a suitable circuit. For this purpose, the valve must be supplied with current during the closing time without resulting in a new lifting of the valve needle.

Opening delay tan and closing delay tab of the valve are preferably determined without brake impulse. The opening delay is defined as the time duration from the beginning of the controlling up to the impact of the armature on the inner pole. Here, preferably the characteristic change in the increase in the current is used as the characteristic feature. Closing delay tab is defined from the end of the controlling without brake impulse up to the impact of the needle on the valve seat. It is preferably determined by evaluating the induction voltage during switching off. Here, the change in the increase in the voltage signal is used as the characteristic feature.

The brake impulse during switching on is determined by the parameters position and duration. The position of the brake impulse during switching on corresponds to time t1. This is determined through the time duration ITO after the beginning of the controlling at time t0. The duration of the brake impulse during switching on corresponds to time duration P0 between times t1 and t2.

These two parameters are preferably determined based on the characteristic feature and, possibly, further characteristic quantities. As the characteristic feature, time ts, or a quantity derived from this time, such as opening delay tan, is used.

This determination preferably takes place in the control device based on the measurement quantities of measurement value ascertaining 120, based on which opening delay tan is ascertained, and based on the sensor signals of sensors 150. As further characteristic quantities, preferably the voltage, the fuel pressure, the intake manifold pressure, and the temperature are used. As voltage, preferably the supply voltage present between terminals 130 and 135 is used. As pressure, preferably the pressure difference between the fuel pressure and the intake manifold pressure is used. As temperature, various temperature values, such as ambient temperature, engine temperature, or fuel temperature can be used. It would be particularly advantageous to use the valve temperature, which can be ascertained either by a sensor or through a suitable model. Through the use of these characteristic quantities in the specification of the position and the length of the brake impulse, there results a substantial reduction in noise emissions.

Preferably, the parameters that determine the brake impulse are stored in one or more characteristic maps, as a function of the characteristic feature and, possibly, the further measurement quantities and/or characteristic quantities.

According to the present invention, it has been recognized that boundary conditions change. For example, opening delay tan changes during operation of the internal combustion engine, or over time due to age-related defects or changing environmental influences. This has the result that the brake impulse no longer occurs at the optimal time.

Therefore, according to the present invention it is provided that opening delay tan is newly ascertained. Standardly, during operation with brake impulse opening delay tan cannot be ascertained immediately, because the switching time in the control phase occurs during time period P0. This has the result that the characteristic current curve cannot be recognized, and therefore cannot be evaluated.

In the extreme case, the changing boundary conditions can have the result that opening delay tan becomes smaller. This can have the result that the characteristic feature in the current occurs already before time t1, i.e., during the phase ITO. In this case, time duration ITO is correspondingly reduced. If changing boundary conditions have the result that opening delay tan becomes larger, then the characteristic feature in the current can occur after time t2. In this case, time duration ITO will correspondingly increase. In these two extreme cases, opening delay tan can be recognized and correspondingly taken into account despite the brake impulse.

FIG. 4 shows the derivative of the current DI plotted over time t. At the beginning, the derivative of the current, which corresponds to the change in the current, has an almost constant value. At time tm, the derivative of the current reaches a maximum, and then falls off. This falling off of the increase is caused by the needle movement. Subsequently, the change again climbs steeply. At the beginning of the falling off of the climb, the flight phase of the needle begins. According to the present invention, a characteristic feature is ascertained that characterizes the beginning of the flight phase. For this purpose, the value dIM of the rise in the current is ascertained. The time tf, at which the rise has fallen off by the value ddl, is used as the beginning of the flight phase of the valve needle. This time tf is used as the characteristic feature instead of time ts. Here, this quantity tf can be used directly as the characteristic feature. Alternatively, the interval taf between time t0 and tf can be used instead of the quantity tan.

The use of the beginning of the flight phase tf is particularly advantageous because this time is before the beginning of the brake impulse and is therefore not influenced by it. In this way, this characteristic feature can supply information about the flight behavior of the valve needle even in braked operation. Therefore, this feature is particularly well-suited for parameterizing the brake impulse.

In FIG. 5a , the current curve at time t0 is plotted over time, and in FIG. 5 the corresponding voltage curve is plotted over time. Voltage U decreases slowly starting from time t0. At time ts, voltage U has a small maximum. Based on this maximum, switching time ts can be ascertained. For this purpose, the voltage is filtered so that disturbing quantities contained in the voltage signal are minimized. By evaluating the derivative of the voltage signal, time ts is ascertained at which the voltage has a local maximum.

In an alternative embodiment, it can also be provided that given a recognized wrong positioning of the brake impulse, a new measurement of opening delay tan is carried out by switching off the brake impulse and ascertaining the characteristic feature.

This means that, based on the measured characteristic feature, a corrected position and/or length of the brake impulse is ascertained.

According to the present invention, when the valve is switched off a brake impulse is also specified. The brake impulse during the switching off is defined by the position and by the duration. The position of the brake impulse during the switching off is defined by time t4, which is defined by the time duration P1 since the end of the controlling at time t3. The duration of the brake impulse at the switching off corresponds to time duration IT2 between times t4 and t5.

The two parameters P1 and IT2, or the position and the duration of the brake impulse, are also set as a function of the closing delay tab as well as further boundary conditions such as voltage, temperature, and pressure. Here as well, the closing delay tab is newly calculated from time to time, similar to the case of the opening delay. The procedure at the brake impulse during switching off is analogous to the procedure for the specification of the brake impulse during switching off. The only difference is that during switching off, closing delay tab is used instead of opening delay tan.

FIG. 6 shows the current curves and voltage curves of a corresponding specific embodiment. At time t4, the brake impulse begins with a rise in the voltage. At the same time, the current increases. At time ts, the valve needle reaches its closed position. This time ts is designated switching time ts, analogous to the specific embodiment according to FIG. 3. The interval between time t4 and time t2 is designated closing delay tab. Closing delay tab is used for the ascertaining of the parameters of the brake impulse during closing, in a manner analogous to the use of the opening delay for the ascertaining of the parameters of the brake impulse during opening of the valve.

Preferably, time t2 is obtained by evaluating the first or second derivative of the current curve. In particular, time ts is recognized at the time at which the first derivative with respect to time of the current curve has a local minimum. 

1-12. (canceled)
 13. A method for controlling at least one switchable valve, the method comprising: producing, during controlling of the valve, a brake impulse that slows down a valve movement of the valve, at least one of a position of the brake impulse, and a length of the brake impulse, being specified as a function of a flight behavior of the valve; and checking whether a characteristic feature occurs that characterizes the flight behavior, and, upon occurrence of the characteristic feature, the position and/or the length of the brake impulse is adapted based on the position of the characteristic feature.
 14. The method as recited in claim 13, wherein at least one of a corrected position of the brake impulse, and a corrected length of the brake impulse, is ascertained based on the characteristic feature.
 15. The method as recited in claim 13, wherein the at least one of the position of the brake impulse, and the length of the brake impulse, are specified as a function of further characteristic quantities, the further characteristic quantities including at least one of a temperature, a pressure, and a voltage.
 16. The method as recited in claim 13, wherein the characteristic feature indicates a switching time.
 17. The method as recited in claim 16, wherein the characteristic feature is a bend in a voltage curve or in a current curve, recognized on the basis of a first derivative of the voltage curve or of the current curve.
 18. The method as recited in claim 16, wherein the switching time is recognized based on a second derivative of a voltage curve.
 19. The method as recited in claim 13, wherein the characteristic feature is a beginning of a flight phase of a valve needle.
 20. The method as recited in claim 19, wherein the beginning of the flight phase is recognized from a first derivative of a current curve.
 21. A machine-readable storage medium on which is stored a computer program for controlling at least one switchable valve, the computer program, when executed by a controller, causing the controller to perform: producing, during controlling of the valve, a brake impulse that slows down a valve movement of the valve, at least one of a position of the brake impulse, and a length of the brake impulse, being specified as a function of a flight behavior of the valve; and checking whether a characteristic feature occurs that characterizes the flight behavior, and, upon occurrence of the characteristic feature, the position and/or the length of the brake impulse is adapted based on the position of the characteristic feature.
 22. A control device designed to control at least one switchable valve, the control device designed to: produce, during controlling of the valve, a brake impulse that slows down a valve movement of the valve, at least one of a position of the brake impulse, and a length of the brake impulse, being specified as a function of a flight behavior of the valve; and check whether a characteristic feature occurs that characterizes the flight behavior, and, upon occurrence of the characteristic feature, the position and/or the length of the brake impulse is adapted based on the position of the characteristic feature. 